The overall purpose of this investigation, situated in a macrocontext of nominal participation of girls in higher- level school mathematics, was to examine, analyse, and describe the way in which a bounded case of Year 10-11 girls viewed their participation in higher-level school mathematics. The focal point of the investigation was the positing of an heuristic model to illuminate why the participants within the bounded case did not wish to participate in higher-level school mathematics. From this model and from the case, it was theorised why some girls avoid higher-level school mathematics; and that, through conceptual generalisations, the heuristic model may help to illuminate, in part, the probability of a girl participating in higher-level school mathematics. This thesis is a construction of the investigation of the beliefs ( perceptions, perspectives, intentions and understandings) of five female secondary students relating to their participation in higher- level school mathematics. An idiosyncratic heuristic case study approach was used to investigate the participants' beliefs. From data analyses and interpretative constructions, it was posited that these girls' beliefs relating to participation in higher-level school mathematics were associated with lifestyle construction, including a balance between the constructed self and constructed life environments. The participants seemed to have constructed a participation ecosystem, consisting of a network of parts, which together formed a balance which influenced their participation choices. Their preferred mathematics construction differed markedly from their higher-level school mathematics construction, and it was apparent that the balance in their lives excluded participation in higher-level school mathematics. From the evidence presented, conceptual generalisations were posited for use in further and broader research purposes, and the heuristic model was viewed as a catalyst for the reconceptualising and reinterpreting of further exploratory models for investigating and explaining participation in school subjects and equivalent.